Soil properties and apricot growth under intercropping and mulching with erect milk vetch in the loess hilly-gully region

Soil in the loess hilly-gully region of northern Shaanxi Province, China, is infertile and rainfall is scarce and uneven. The objectives of this study were to improve soil quality, promote apricot (Prunus armeniaca L.) growth, and assess whether erect milk vetch (Astragalus adsurgens Pall.) and apricot compete for soil moisture and soil nutrients under intercropping systems. Taking clean tillage as the control, soil moisture and soil nutrients were monitored in apricot orchards in which erect milk vetch was interplanted for 5 years and interplant-mulched and mulched for 4 years. Intercropping and intercrop-mulching with erect milk vetch reduced soil moisture and soil nutrients and decreased fruit yield, fruit weight, and economic output. Mulching with erect milk vetch increased soil moisture in the 0-60-cm soil layer; increased soil organic matter, total N, and soil-available nutrients in the 0-20-cm soil layer; and increased fruit yield, fruit weight, and economic output. Under intercropping and intercrop-mulching, erect milk vetch and apricot competed for soil moisture and soil nutrients. Intercropping and intercrop-mulching with erect milk vetch are inappropriate, but mulching with erect milk vetch is a suitable method for managing soil quality in apricot orchards in the loess hilly-gully region.